The present invention relates to a camera with a zooming mechanism.
Various kinds of automatic compact cameras, which have become very popular, are provided with an automatic film transporting feature and an automatic focusing feature. In recent years, certain kinds of such automatic compact cameras have even been provided with zoom lenses.
Zoom lenses are continuously variable in focal length. To vary the focal length of a zoom lens, a zooming mechanism includes a movable lens barrel holding therein a zoom lens system and a fixed lens barrel slidably receiving therein the movable lens barrel. When moving the movable lens barrel in an axial direction of the zoom lens system within the fixed lens barrel, the zoom lens system shifts its component lens groups following a predetermined relationship between the lens groups.
A camera body with a lens barrel fixedly mounted therein is usually provided with a driven sprocket which is driven by a film in the camera to control the advance of the film and to count exposures, and a drive sprocket which drives the film by a predetermined length immediately after the film is loaded and the back cover of the camera is closed. The provision of these sprockets makes the camera body bulky or thick. In an attempt to avoid such bulkiness or thickness of the camera, the rear ends of the outer and inner lens barrels should not overlie the sprockets.
However, locating the sprockets on one or both sides of the fixed or outer lens barrel increases the distance between the film supply chamber and the film take-up chamber of the camera, and as a result the camera is still bulky.
To change the focal length of the zoom lens system suitably for wide-angle photography, a rear lens group of the zoom lens system is moved toward a plane in which an exposure aperture is formed. Moreover, in collapsible-mount-type cameras, it is almost always necessary to move the rear lens group farther to the rear from the position wherein the zoom lens system has a focal length suitable for wide-angle photography. However, structure such as driving and driven sprockets projecting from the plane in which the exposure aperture is formed, prevents the rear lens group from moving back sufficiently and so it is still difficult to avoid bulkiness or undesirable thickness of the camera.
To reduce the thickness of the camera body, it has been proposed to reduce the size of the sprockets. However, a small diameter of driving sprocket is apt to break the perforations of the film.
Another problem with such a camera with a zoom lens is the structural strength of the zoom lens driving mechanism, which should be compact and should perform zooming operations with high accuracy. In particular, the zoom lens driving mechanism should allow fine adjustment of the focus of the zoom lens for any focal length upon assembling the zoom lens in the camera.